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have been applied at the moment of death, and have shown no sign. Now it is certain of the forces of heat, light, motion, &c., that they are absolutely indestructible : they may be converted one into another, but they cannot cease to exist. If the vital principle was analogous to these agencies it might escape in any one of them ; but of this no well ascertained trace has been observed in any investigation of the phenomena of death.

The uniformity of the period through which life extends in any given species is a result that no one would anticipate if the vital principle be of the nature of the known forces. The physical elements of animals are said to undergo an entire renewal in the course of a few years. Surely, then, with renewed materials to work upon, and with something akin to the imponderables to do the work, animals should never grow old. Why should they-any more than oxygen should lose its vigour and grow tired of uniting with hydrogen ?

We have now noticed some of the considerations which appear to favour the supposition that the vital principle is a thing sui generis. 1st, the unparalleled hiatus which exists between things

animate and things inanimate. 2nd, the great dissimilarity between the properties of the

imponderables and those of vitality. 3rd, the difficulty arising from the hypothesis that the

embryo of a living thing is developed only by agencies

analogous with known forces. 4th, the permanence of form and structure observable

during many generations of the same species. 5th, the absence of any indications as to what becomes of

the vital principle at death. 6th, the periodicity of life.

It is not contended that these considerations amount to a demonstrative proof that the vital principle is a thing sui

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generis, but the question naturally arises, how far, supposing our conclusion to be a right one, a demonstrative proof is possible.

An instance somewhat parallel may be found in the field of Natural Theology, in which is assumed, as a starting-point, the existence of a first supreme Cause, whose nature is beyond all comprehension; certain facts are adduced which agree with this assumption; also its rejection is shown to involve many great difficulties; but all this is not proof; and in fact proof here seems to be out of the question, for the simple reason that whatever that might be of which the existence could be proved, it would not be the infinite one. In logic, as in mechanics, action and reaction are equal, and the very locus standi required by a proof, in the thing to be proved, puts demonstration in this case out of the question. Similarly, if the existence of vitality as a distinct thing were capable of being demonstrated by direct proof, the vital principle must be of the nature of other agencies, which is contrary to the original hypothesis.

It would be very interesting to trace the course of those discoveries in physiology which have led some eminent observers to class vitality with other known forces. It cannot be denied that a very large number of facts connected with the phenomena of life, formerly supposed to be attributable only to the undefined agency of the vital principle, are now accounted for on principles which are purely scientific. For example, the constituents of some of the proximate elements of organic substances, such as starch, albumen, &c., were known long ago ; but the power to combine these constituents so as to produce the proximate elements was regarded as being possessed by the vital principle alone, the working of which in the formation of the proximate elements could, it was thought, by no means be imitated in the laboratory. This is now known to be an error ; the chemist by his science does that which before was considered to be the peculiar function of the vital principle. In these and many other instances, it has been proved that the aid of the vital principle has been unnecessarily invoked to account for results explicable on scientific grounds.

In all this we have a parallel to that which has taken place in the more extensive field of the Cosmos. Yet there are some who are conscious that if it were possible to trace the existing state of things by a regular series of scientific deductions to a nebular condition of the universe, no appproach would be made thereby to the possibility of dispensing with a first supreme cause.

It is, however, abundantly evident that the great Originator of nature has chosen to accomplish his purpose by a wondrous succession of fixed laws, open to our investigation, and revealing depth beyond depth to a most remote and obscure profundity.

With this fact before us, on the hypothesis that the force of life, like its author, possesses an unknown, perhaps an unknowable nature, we should not expect its interposition to be conspicuous; we should, I think, expect its agency to be executed only behind a succession of fixed laws, forming a vista, having its termination almost lost in the distance. The natural evidence in the two cases must of necessity, as we have seen, be of the same character, not direct nor demonstrative, but implied and inferential.

Whatever weight may be due to the considerations here urged in favour of the speciality of the vital principle, at all events they answer these expectations and conditions. Those arguments on which most stress has been laid arise at points where, if evidence be possible, any one who thinks at all on the subject, would expect to find it. Something altogether unusual in nature marks the boundary of the province in which life-force prevails; and the phenomena of life do not

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submit to be accounted for under the rigid laws which govern the application of all forces that are known.

Since the greater part of the above was written I obtained the first number of the Quarterly Journal of Science, in which appears a paper by Dr. Carpenter, part first, “On the relations of Light and Heat to the Vital Forces of Plants." The views of so eminent an authority will everywhere command attention and respect, and it was not a little gratification to myself to find that on the whole they were consistent with those expressed in this paper.

By far the greater portion of Dr. Carpenter's paper is taken up with matters perfectly compatible with, but having no direct bearing upon the question we have had before us. In one short sentence, however, he thus states and illustrates his views on the point in question:

The history of a living organism then is one of incessant change, and the conditions of this change are to be found partly in the organism itself, and partly in the external agencies to which it is subjected. That condition which is inherent in the organism being derived hereditarily from its progenitors, may be conveniently termed its germinal capacity : its parallel in the inorganic world being that fundamental difference in properties which constitutes the distinction between one substance, whether elementary or compound, and another; in virtue of which each behaves in its own characteristic manner when subjected to new conditions.”

That which I have spoken of as the vital principle, Dr. Carpenter here seems to denominate the “ germinal capacity;" but without attempting a definition of the germinal capacity, he gives an illustration which amounts to this :-That the germinal capacity of one living thing, differs from that of another living thing as an atom of hydrogen differs from an atom of oxygen.

We do not require an illustration to be perfect in all respects, and, on the

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whole, this one seems to me to answer its purpose.

But if it be contended that the illustration goes much deeper than I have represented, then in reply, I must urge, with the highest respect for the author, that the sentence is not so lucid as I am sure Dr. Carpenter himself would wish it to be ; that a capacity cannot be parallel to a fundamental, or any other difference ; and that certainly it cannot be Dr. Carpenter's meaning to compare the germinal capacity of an organism with the atomic properties of an inorganic substance, when, according to his own showing, the former produces incessant changes ;” the latter, permanent combinations; the former is derived heriditarily from its progenitors ;" the latter can in no sense be said to have had progenitors; the former is the inherent condition,the latter the chief source of the influence of external agencies.

In fact nothing can be more satisfactory to myself than the distinction which Dr. Carpenter in another part of his paper draws between heat as the constructive force" and the

germinal capacity," the vital principle of this paper, as the directive agency in the development of the living organism. He compares the germinal capacity to the control exercised by the superintendent builder who is charged with the working out the design of the architect! Heat he compares to the bodily force of the workmen who labour under his guidance. in the construction of the fabric.

This is indeed saying all that I would wish to say much better than I could myself have expressed it. The only remaining question is, will other physiologists be content with this-content to leave far out of the reach of their correlative forces the vital principle, the “germinal capacity,” the working of the "superintendent builder charged with the execution of the design of the architect." I think not, and therefore, I venture to submit, the arguments of the preceding paper are not needless; for it may be remarked of the nature of the

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